How to change thickness of Line()

[Gedicht2von101]

I need to get thinner lines than i get with this code:

from manim import *

class Bulgarian(Scene):

    def construct(self):

        title = Tex(r"\centering Geometry problem\\ from 1997 Bulgarian MO", font_size=48)

        self.play(Write(title), run_time=2.5)
        self.wait(1.5)
        self.play(FadeOut(title, shift=DOWN),run_time=1.5)
        
        dotA = Dot([-6,-1.01,0], .04, stroke_width=0.5).set_fill(WHITE).set_stroke(BLACK).set_stroke_opacity(0.5)
        dotB = Dot([4-6,-1.01,0], .04, stroke_width=0.5).set_fill(WHITE).set_stroke(BLACK).set_stroke_opacity(0.5)
        dotC = Dot([4.4406-6,2.0366-1.01,0], .04, stroke_width=0.5).set_fill(WHITE).set_stroke(BLACK).set_stroke_opacity(0.5)
        dotA1 = Dot([4.19835-6,0.91685-1.01,0], .04, stroke_width=0.5).set_fill(WHITE).set_stroke(BLACK).set_stroke_opacity(0.5)
        dotB1 = Dot([2.91961-6,1.33902-1.01,0], .04, stroke_width=0.5).set_fill(WHITE).set_stroke(BLACK).set_stroke_opacity(0.5)
        dotC1 = Dot([6.97545-6,-1.01,0], .04, stroke_width=0.5).set_fill(WHITE).set_stroke(BLACK).set_stroke_opacity(0.5)
        dotA2 = Dot([5.48467-6,1.19774-1.01,0], .04, stroke_width=0.5).set_fill(WHITE).set_stroke(BLACK).set_stroke_opacity(0.5)
        dotPhantom = Dot([5-6,2.29315-1.01,0])


        title = Tex(r"\begin{minipage}{7cm} Given:\\ $\triangle$ $ABC$; $AA_1$,$BB_1$, $CC_1$ are bisectors;\\ To proof:\\ $AB$, $A_1B_1$, $CC_1$ are intersecting in one point or parallel. \end{minipage}", font_size=20).next_to([1.5,0,0])

        Atext = MathTex("A", font_size=20).next_to(dotA, (0.5)*DOWN).set_color(YELLOW)
        Btext = MathTex("B", font_size=20).next_to(dotB, (0.5)*DOWN).set_color(YELLOW)
        Ctext = MathTex("C", font_size=20).next_to(dotC, (0.5)*UP).set_color(YELLOW)
        A1text = MathTex("A_1", font_size=20).next_to(dotA1, (0.25)*RIGHT + (0.43)*DOWN).set_color(YELLOW)
        B1text = MathTex("B_1", font_size=20).next_to(dotB1, (0.5)*UP).set_color(YELLOW)
        C1text = MathTex("C_1", font_size=20).next_to(dotC1, (0.5)*DOWN).set_color(YELLOW)
        A2text = MathTex("A_2", font_size=20).next_to(dotA2, (0.25)*RIGHT + (0.43)*UP).set_color(YELLOW)

        lineA = Line(dotB.get_center(), dotC.get_center()).set_color(BLUE)
        lineB = Line(dotC.get_center(), dotA.get_center()).set_color(BLUE)
        lineC = Line(dotA.get_center(), dotB.get_center()).set_color(BLUE)
        lineC1 = Line(dotC.get_center(), dotPhantom.get_center()).set_color(BLUE)
        lineA1 = Line(dotA.get_center(), dotA1.get_center()).set_color(BLUE)
        lineB1 = Line(dotB.get_center(), dotB1.get_center()).set_color(BLUE)

        dlineA = DashedLine(dotB.get_center(), dotC1.get_center(), dash_length=0.2).set_color(BLUE)
        dlineB = DashedLine(dotB1.get_center(), dotC1.get_center(), dash_length=0.2).set_color(BLUE)
        dlineC = DashedLine(dotC.get_center(), dotC1.get_center(), dash_length=0.2).set_color(BLUE)
        dlineA1 = DashedLine(dotA1.get_center(), dotA2.get_center(), dash_length=0.2).set_color(BLUE)
        dlineC1 = DashedLine(dotB.get_center(), dotA2.get_center(), dash_length=0.2).set_color(BLUE)

        angA_1 = Angle(lineC, lineA1, .5, (1,1), color=BLUE)
        angA_2 = Angle(lineA1, lineB, .6, (1,-1), color=BLUE)
        angB_1 = VGroup(Angle(lineA, lineB1, .2, (1,1), color=BLUE), Angle(lineA, lineB1, .3, (1,1), color=BLUE))
        angB_2 = VGroup(Angle(lineB1, lineC, .25, (1,-1), color=BLUE), Angle(lineB1, lineC, .35, (1,-1), color=BLUE))

        angC_1 = VGroup(Angle(lineA, dlineC, .2, (-1,1), color=BLUE),
                        Angle(lineA, dlineC, .3, (-1,1), color=BLUE),
                        Angle(lineA, dlineC, .4, (-1,1), color=BLUE))
        angC_2 = VGroup(Angle(dlineC, lineC1, .25, (1,1), color=BLUE),
                        Angle(dlineC, lineC1, .35, (1,1), color=BLUE),
                        Angle(dlineC, lineC1, .45, (1,1), color=BLUE))

        angD_1 = Angle(dlineA, dlineC1, .4, (1,1), color=BLUE, dot = True, dot_radius= .03, dot_color=BLUE)
        angD_2 = Angle(dlineC1, lineA, .5, (1,1), color=BLUE, dot = True, dot_radius= .03, dot_color=BLUE)

        self.add_foreground_mobjects(dotA, dotB, dotC, dotA1, dotB1, dotC1)

        self.play(AnimationGroup(AnimationGroup(Write(dotA), Write(Atext), lag_ratio=0.5), Write(lineC),
                                 AnimationGroup(Write(dotB), Write(Btext), lag_ratio=0.5), Write(lineA),
                                 AnimationGroup(Write(dotC), Write(Ctext), lag_ratio=0.5), Write(lineB),
                                 AnimationGroup(Write(lineA1), Write(angA_1), Write(angA_2), lag_ratio=0.5),
                                 AnimationGroup(Write(dotA1), Write(A1text), lag_ratio=0.5),
                                 AnimationGroup(Write(lineB1), Write(angB_1), Write(angB_2), lag_ratio=0.5),
                                 AnimationGroup(Write(dotB1), Write(B1text), lag_ratio=0.5), Write(title),
                                 AnimationGroup(Write(dlineA), Write(dlineB), Write(lineC1), Write(dlineC), Write(angC_1), Write(angC_2), lag_ratio=0.5, run_time=3.5),
                                 AnimationGroup(Write(dotC1), Write(C1text), lag_ratio=0.5), lag_ratio=0.95, run_time=17))
        self.wait(3)

        PROOF1 = Tex(r"\begin{minipage}{8cm} Proof: $$\text{if}\;\;\;\frac{AB_1}{B_1C}\cdot\frac{CA_1}{A_1B}\cdot\frac{BC_1}{C_1A}=\frac{AC}{BC}\cdot\frac{BC_1}{C_1A}=1,$$ $A_1$, $B_1$ and $C_1$ is on one straight line; \end{minipage}", font_size=20).next_to([1.5,2.675-1.75,0])
        PROOF2 = Tex(r"\begin{minipage}{8cm} $A_2$ is center of escribed circle $\Rightarrow$ \end{minipage}", font_size=20).next_to([1.5,1.8-1.7,0])
        PROOF3 = Tex(r"\begin{minipage}{8cm} $BA_2$ is bisector os $\angle CBC_1$ $\Rightarrow$ \end{minipage}", font_size=20).next_to([1.5,1.575-1.75,0])
        PROOF4 = Tex(r"\begin{minipage}{8cm} $\dfrac{CA_2}{A_2C_1}=\dfrac{AC}{AC_1}$, $\dfrac{CA_2}{A_2C_1}=\dfrac{BC}{BC_1}$ $\Rightarrow$ $\dfrac{AC}{BC}\cdot\dfrac{BC_1}{C_1A}=1.$\end{minipage}", font_size=20).next_to([1.5,1.125-1.75,0])
        
        self.add_foreground_mobject(dotA2)

        self.play(AnimationGroup(Transform(title, PROOF1), AnimationGroup(Write(dlineA1), AnimationGroup(Write(dotA2),Write(A2text), lag_ratio=0.5), Write(PROOF2), lag_ratio=0.95),
                  AnimationGroup(AnimationGroup(Write(dlineC1), Write(angD_1), Write(angD_2), lag_ratio=0.5), Write(PROOF3), lag_ratio=0.95),
                  Write(PROOF4), lag_ratio=0.95, run_time=15))
        self.wait(3)

Bulgarian.mp4

[behackl]

The width of the stroke is controlled via the stroke_width keyword argument. The default stroke width value is 4, so anything below that will result in thinner lines; e.g. Line(A, B, stroke_width=2).

If you want to set it consistently for all Line objects, run Line.set_default(stroke_width=2), for example. Hope this helps!

[Gedicht2von101]

Thank you so much!